ISC DHCP client/Ubuntu fails to connect to commercial routers and code fix suggestion
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| isc-dhcp (Ubuntu) |
New
|
Undecided
|
Unassigned | ||
Bug Description
Linux systems (Ubuntu 16.04) fail to connect to various hotels with wifi as a result of the DHCPDiscover message being sent by dhclient. The same laptop using MSWindows connects with the hotels without a problem. This has been observed at multiple locations.
The problem was isolated by making the DHCPDiscover packet sent by dhclient match the DHCPDiscover packet sent by MSWindows. It was found that affecting difference was that dhclient generated a non-zero value for the TOS UDP field. Commenting out the setting of ip.ip_tos in packet.c so that the field remained zero fixed the problem:
dhcp-4.4.1/common:
$ diff packet.c packet.c.orig
150c150
< // ip.ip_tos = IPTOS_LOWDELAY;
---
> ip.ip_tos = IPTOS_LOWDELAY;
The hotel's router may have been misconfigured to interpret the TOS field. However, the hotel connects to MSWindows/Apple devices. As a result, open source systems such as Ubuntu (Linux) gain a reputation of being unreliable. (My wife wants/needs to use MS/Apple systems as result)
I would like to suggest that if the default DHCP message content generated by MSWindows/Apple adheres to standards, then the default DHCP message content from open source systems (linux) match bit for bit. Sniff packets and compare to verify. Such practice would assure that open source connectivity (linux) is no less reliable than commercial device connectivity.
